Possible Clues:

• Collar gunmen's oil supplier
• The kernel of an oily business is chasing crooks registered by middleman
• Source of oil to provide power in my area
• Desiccated coconut?
• Garda artist is a bit of a dry nut
• Dried Coconut
• Constable, perhaps, wanting artist's source of oil
• Constable and another artist needed source of oil
• Start of probe in well, a source of oil
• Shell offering oil company fifty per cent of European capital